The application of various mass spectrometric techniques to structure elucidation of three classes of biologically important natural products will be studied. The first group encompasses novel marine sterols, which differ primarily from terrestrial sterols in the nature of their unusual (elongated or branched) side chains. This feature appears to be of importance in cell membrane function and a detailed knowledge of the mass spectral fragmentation pattern of such sterol types is needed for structural elucidation of novel and as yet unidentified sterols of marine organisms. Much of this work requires synthesis of requisite sterol reference compounds or synthetic verification of postulated structure. The second group of natural products deals with the unusual phospholipids isolated from marine organisms. Much less is known about the mass spectrometric behavior of this biologically important class of natural products as compared to sterols, and we intend to explore this field in detail by comparing different ionization techniques (electron impact vs. field desorption vs. chemical ionization vs. fast atom bombardment) since each is likely to provide special structural information on specific portions of the phospholipid molecule. Since the novel marine phospholipids are particularly unusual in the context of their unprecedented fatty acid components (usually polyunsaturated), work is also envisaged on the mass spectrometric location of such double bonds in long-chain fatty acids. Finally, we intend to develop mass spectral procedures (notably through the use of chemical ionization mass spectrometry with hydrogen gas) in the porphyrin field with the aim of accomplishing an as yet largely unrealized goal, namely the location of chemical substituents in the four different pyrrole rings of the prophyrin molecule solely through the use of mass spectrometry. If successful, this should not only make an important contribution to porphyrin chemistry, but should also help greatly in drug metabolism studies involving cytochrome P-450.